Chin J Plant Ecol ›› 2022, Vol. 46 ›› Issue (8): 890-903.DOI: 10.17521/cjpe.2021.0363

Special Issue: 碳水能量通量

• Research Articles • Previous Articles     Next Articles

Water vapor fluxes and their relationship with environmental factors in a conifer-broadleaf mixed forest ecosystem in Jinyun Mountain, Chongqing, China

FENG Yin-Cheng1, WANG Yun-Qi1,*(), WANG Yu-Jie1, WANG Kai1, WANG Song-Nian1, WANG Jie-Shuai2   

  1. 1Chongqing Jinyun Mountain Three Gorges Reservoir Area Forest Ecosystem Positioning Observation and Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China
    2Forestry Station of Suzhou High Tech Zone, Suzhou, Jiangsu 215011, China
  • Received:2021-10-12 Accepted:2022-03-21 Online:2022-08-20 Published:2022-04-22
  • Contact: WANG Yun-Qi


Aims This study aimed to examine the practicability of eddy covariance method in a conifer-broadleaf mixed forest ecosystem in Jinyun Mountain of Chongqing, China, and to analyze the dynamics of water vapor flux in this forest ecosystem. Meanwhile, the main environmental factors that influence water vapor flux was also discussed. Our results may provide a case for such study in forest water vapor budget.

Methods The eddy covariance method was used to continuously observe the vapor fluxes and meteorological factors from September 2019 to August 2020 in a conifer-broadleaf mixed forest. The original data of water vapor flux was corrected and interpolated by Eddy Pro software. We used these data to analyze the energy closure and variation of water vapor fluxes, and as well as environmental factors.

Important findings (1) The energy closure rate in our study forest is 0.77. The direction of the high contribution area of flux footprints in such forest is similar to the annual main wind direction (northeast), indicating that the method of vorticity related technology is practicable and reliable in this kind of forest. (2) In our study forest, the annual water vapor flux is over zero, and the monthly average daily variation is -0.001-6.623 mmol·m-2·s-1, suggesting that this forest is a source of water vapor in study area. There is a single peak trends for monthly average daily variation and seasonal variation of water vapor fluxes. By contrast, the average value of water vapor fluxes is the highest (4.620 mmol·m-2·s-1) in summer with strong fluctuations, and the lowest (2.077 mmol·m-2·s-1) in winter with weak fluctuations. (3) The total annual evapotranspiration (792.40 mm) in this forest accounts for 53.12% of the total precipitation (1 489.18 mm), and the summer evapotranspiration (325.53 mm) and precipitation (680.52 mm) are the highest, accounting for the annual evapotranspiration and precipitation respectively 41% and 46%. Compared with other ecosystem sites, we found that total annual evapotranspiration was less in our study forest than in wetland, but more than in farmland and grassland. (4) The water vapor flux was positively correlated with net radiation, air temperature and vapor pressure deficit. Such correlations (R2) were the highest in summer, and reached to 0.85, 0.53 and 0.60, respectively. Conversely, the water vapor flux was negatively correlated with wind speed, and the R2 equal to 0.61 in the summer. It seems likely that net radiation and air temperature are the main drivers in water circulating at our study forest.

Key words: conifer-broadleaf mixed forest, water vapor flux, eddy correlation, evapotranspiration, net radiation